The invention relates to a layer containing carbon and a method and apparatus for producing a layer containing carbon on a substrate by means of sputtering.
In electron-microscopic imaging of specimens which consist of insulating material, charges and contaminations occur on the surfaces of the specimens to be imaged as a result of the electron bombardment. These charges and contaminations deteriorate the image quality.
In order to avoid charges on surfaces of the insulating material to be imaged, until now the energy of the electron beam had to be set such that the number of electrons impinging the specimen was equal to the number of emitted electrons, namely the secondary electrons together with the backscattered electrons. When it was not possible to set the energy of the primary electron beam so that the number of electrons impinging the specimen was equal to the number of electrons emitted from the surface to be imaged, the metallic layer allowed the excess charge to discharge and thus helped to avoid a charging of this surface during the irradiation of the surface with the primary electron beam. When this metallic layer was applied to a surface to be imaged in order to prevent charging, it was kept very thin, for example less than 1 nm. Then the charging could be reduced as a result thereof given imaging of surface wave components, for example without the function of these surface wave components being deteriorated. The method of applying a metallic layer for the prevention of charging to a surface to be imaged can be utilized in imaging surface wave components up to frequencies of about 300 MHz. High-frequency shorts which can be observed given both surfaces of surface wave components to be imaged, as well as surfaces of integrated circuits wherein the switching times amount to a few nano seconds, occur at higher frequencies.
In addition to the charging of surfaces to be imaged, contaminations on surfaces to be imaged also deteriorate the image quality. Contaminations can in fact be avoided by means of an oil-free vacuum and by means of a special cleaning of the specimens to be imaged. In electron beam measuring techniques, however, these conditions of an oil-free vacuum and of a special cleaning of the specimens to be imaged cannot be practically met.
Biological, medical or other specimens such as, for example, paper or glass, or ceramic or other surfaces which consist of insulating materials or of materials on which a disruptive contamination can occur, should also be capable of being electron-microscopically imaged. Since metallic layers adhere very poorly to some surfaces which are to be imaged, for example ceramic, a means is required above and beyond use of metallic layers which, on the one hand, aids in preventing charges and contaminations and, on the other hand, adheres well to nearly every possible substrate.